• Structural Engineering and Mechanics
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• 제51권5호
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• pp.847-866
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• 2014

This paper describes a formulation to predict optimum post-tensioning forces and cable dimensioning for self-anchored cable-stayed suspension bridges. The analysis is developed with respect to both dead and live load configurations, taking into account design constrains concerning serviceability and ultimate limit states. In particular, under dead loads, the analysis is developed with the purpose to calculate the post-tensioning cable forces to achieve minimum deflections for both girder and pylons. Moreover, under live loads, for each cable elements, the lowest required cross-section area is determined, which verifies prescriptions, under ultimate or serviceability limit states, on maximum allowable stresses and bridge deflections. The final configuration is obtained by means of an iterative procedure, which leads to a progressive definition of the stay, hanger and main cable characteristics, concerning both post-tensioning cable stresses and cross-sections. The design procedure is developed in the framework of a FE modeling, by using a refined formulation of the bridge components, taking into account of geometric nonlinearities involved in the bridge components. The results demonstrate that the proposed method can be easily utilized to predict the cable dimensioning also in the framework of long span bridge structures, in which typically more complexities are expected in view of the large number of variables involved in the design analysis.

• 대한건축학회논문집:구조계
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• 제34권11호
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• pp.19-26
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• 2018

This paper presents the shear strengthening effect of externally post-tensioning (EPT) method using high-strength steel rod in pre-cracked reinforced concrete (RC) beams. Three- and four-point bending tests were performed on a total of 8 specimens by adjusting the strengthening depths in the deviator position of EPT. The effective strengthening depths were 435, 535, and 610 mm. The pre-loading up to about 2/3 of ultimate load capacity measured in unstrengthened RC beam were applied in the beam to be post-tensioned. The EPT method was then applied to the pre-damaged RC beams and re-loading was added until the end of the test. EPT restored deflections of 3 mm or more, which account for about 40% of deflection when the pre-loading was applied. The shear strengthening increases more than 3 times and 36~107% in terms of the stiffness and load-carrying capacity compared to unstrengthening RC beams. The increased load-carrying capacities of the post-tensioned beam with strengthening depths of 435 and 535 mm are almost the same as 36~61%, and those of 610 mm are 84~107%, which shows the greatest shear strengthening effect.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1168-1173
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• 2004

Bridges and tunnels mainly compose the structural system of Kyung-bu high-speed railway in Korea and the prestressed concrete box girder bridges are applied for the most part of bridge structures. Precast full span construction method was practiced in the construction of many prestressed concrete box girder bridges in Kyung-bu high speed railway for the high quality, great construction speed, low construction cost and construction safety. However, there have been no application of this method in continuous bridges until now. Therefore, a new advanced precast full span construction method is developed using pre-tensioning for precast and post-tensioning in alternating the simple span into a continuous bridge system. since the high-speed railway trains can cause dynamic problems in a continuous bridge. This study shows the structural behavior and the construction process of the new advance method.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.40-43
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• 2004

A new design method for prestressed concrete girder is proposed in this study, which steps for manufacturing are; (1) the bottom part of concrete girder is placed and pretensioned by the first post-tensioning performed on the tendons located in the bottom part of concrete girder, and (2) the next step which consists of concrete placing and post-tensioning operation is followed by the previous step if required. This indicates that sufficient compressive stress can be effectively introduced at the bottom face in stepwise manner, when compared to conventional PSC girder. Two specimens are prepared and tested to investigate the short-term behavior of the PSC girders manufactured by the proposed method. Section Analysis results exhibit good agreements with the test results in terms of strain distribution across the girder section. In addition, flexural strength obtained from the tests is found to be similar to the expected based on Code(Korea). These demonstrate that the method proposed in this study is applicable to the design of PSC girders.

• 대한관절경학회지
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• 제3권2호
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• pp.102-108
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• 1999

목 적 : 술 전 장력유지 장치를 사용하지 않고 동종 골-슬개건-골 이식건으로 전방십자인대 재건술을 시행한 후 임상적 결과를 조사하여 보았다. 대상 및 방법 : 동종 골-슬개건-골 이식건을 이용 관절경하에 전방십자인대 재건술을 시행한 환자 중 2년 이상 추시가 가능한 43명, 46례로 주관적, 객관적 지표, Telos stress arthrometer, modified Feagin Scoring System을 이용해 분석하였다. 수술 시 평균 연령은 27세(18~42세), 평균 추시 기간은 41개월(24~79개월)이었다. 동종 골-슬개건-골 이식건은 술 전에 재수분화 시켰으며, 술 전 장력유지 장치를 이용한 장력은 주지 않았고, 관절경하에서 이중터널 방법을 이용하여 이식건을 이식하고, 슬관절 굴곡 및 신연을 통한 이식건의 장력을 주고 간섭 나사못을 사용하여 고정하였다. 결 과 : Lysholm knee score는 술 전 60점에서 84점으로 24점 증가를 보였고, Telos arthrometer를 이용한 전방 스트레스 단순 방사선 사진상 술 전 7.1mm에서 술 후 2.3mm로 향상되었다. 추시 상 슬관절 운동능력은 정상이었고, 신전 시 굴곡 구축은 보이지 않았으며, modified Feagin Scoring System상 양호 이상이 39례(84.7%)이었다. 결 론 : 동종 골-슬개건-골 이식건을 이용한 전방십자인대 재건술의 임상적 결과는 자가 골-슬개건-골 이식건을 이용한 방법에 비해 큰 차이를 보이지 않았으며, 수술 전의 장력유지 장치를 사용하지 않아도 임상적으로 큰 영향이 없었다. 따라서 동종 골-슬개건-골 이식건은 여러 가지 문제점을 지닌 자가 골-슬개건-골 이식건의 대용으로 사용이 기능할 것으로 사료된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
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• pp.797-802
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• 1997

The current study is a part of series o research about the development of new superstructure system to overcome the engineering problems in the design of bridges of 30m to 45m in span length using the existing bridge systems. The basic concept of new system is the continuation of adjacent tow simple spans composed of the precast prestressed concrete U-type sections. The partial post tensioning method is applied to create the continuity. In this study, the new technique was introduced and applied with an example design of tow span of 40m in span length to find the possibility for practical application as the feasibility study. The obtained results show that the new splicing method is expected to offer significant economical and serviceability advantages.

• Structural Engineering and Mechanics
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• 제6권6호
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• pp.693-710
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• 1998

This paper concerns studies on the shape formation of post-tensioned and shaped steel domes. The post-tensioned and shaped steel domes, assembled initially at ground level in an essentially flat condition, are shaped to a curved space form and erected into the final position by means of a post-tensioning technique. Based on previous studies on this shape formation principle, three post-tensioned and shaped steel domes have been constructed. The results of the shape formation tests and finite element analyses are reported in this paper. It is found that the first two test domes did not furnish a part-spherical shape as predicted by finite element analyses, because the movements of some mechanisms were not controlled sufficiently. With a revised post-tensioning method, the third dome obtained the theoretical prediction. The test results of the three post-tensioned and shaped domes have shown that a necessary condition to form a desired space shape from a planar layout with low joint stiffnesses is that the movements of all the existing mechanisms must be effectively controlled as indicated by the finite element analysis. The extent of the maximum elastic deformation of a post-tensioned and shaped steel structure is determined by the strength of the top chords and their joints. However, due to the semi-rigid characteristic of the top chord joints, the finite element analyses cannot give a close prediction for the maximum elastic deformations of the post-tensioned and shaped steel domes. The results of the current studies can be helpful for the design and construction of this type of structure.

• 한국강구조학회 논문집
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• 제9권3호통권32호
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• pp.441-455
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• 1997

많은 나라에서 기 시공된 교량의 보수 보강에 대한 관심이 고조되고 있고 많은 보고서와 인쇄물에서 이에 대해 강조되고 있다. 국내의 1960년대와 1970년대 사이에 시공된 교량은 상대적으로 적은 차량크기, 속도, 중량으로 설계되어 현재의 교통조건에 부적절하다. 다소의 설계오류와 함께 이는 많은 교량의 여러 결함을 유발한다. 보수 보강의 한 방법으로 많은 잇점을 가진 external post-tension tendon을 사용하는 것이고 본 논문에서 external post-tension을 이용한 3경간 연속 합성교량의 보강방안에 대해 기술한다.

• 한국구조물진단유지관리공학회 논문집
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• 제7권1호
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• pp.157-163
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• 2003

Recently, the number of Prestressed Concrete(PSC) bridges needed repair and retrofit because of the increase of heavy traffic loads and aging of concrete materials. But there are a few related researches about strengthening PSC bridges. In this study, the practicability of strengthening methods for PSC beam were studied by the static experimental method. PSC beams in length of 6m were made with concrete slabs. Glass fiber sheeting and external post-tensioning methods were used for strengthening PSC beams. Some beams were strengthened after cracks to investigate the applicability for cracked bridges. As a result, there strengthening methods were efficient at increasing the cracking loads and the failure load, to decrease deflection and prevent cracks. In the case of using glass fiber retrofit methods, it should be careful in the anchorage problems for preventing the bonding failure.

• 한국구조물진단유지관리공학회 논문집
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• 제7권1호
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• pp.165-172
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• 2003

The fatigue problem of Prestressed Concrete(PSC) bridges are more serious than the other type of concrete bridges, because the cross sectional area and self weight of PSC bridges are smaller. The endurance of strengthening methods for PSC bridges are tested in this study. Glass fiber sheeting and external post-tensioning methods were applied. 1/5 scale PSC beams were made for fatigue test, same as static test. The range of repeated load is from 10% to 80% of yielding load with sine curve. The experimental results show that the failure cycle of strengthened members are increased compare to non-strengthened members. The members strengthened with glass fiber show better enhancement in fatigue problem than the members strengthened with external post-tensioning method, though the adhesion of glass fiber and concrete is failed, as increase of crack. With these experimental results, it can be said that the strengthening methods used in this study are efficient at extending the life time of aged PSC bridges.